First of all, before you make any mistakes you might regret, you'll have to install 3.03 OE-A or 3.03 OE-A'. This doesn't matter. I'm not 100% certain if the second one is simply an update or a stand-alone custom firmware.

I can't supply you with an easy installer because I don't know of any just yet (there's probably one somewhere) but I'd recommend starting here: http://dark-alex.org/ the official website for Dark_Alex, the creator of the custom firmware.

Download 3.03 OE-A (to be safe, as I say I can't be sure if 3.03 OE-A' is stand-alone or not) and follow the instructions in the readme or follow the instructions given by Dark_Alex on the thread the download is in.

Note: Follow ALL the instructions given by Dark_Alex, including the actual installation on the PSP itself, the nasty bit which flashes your PSP. Don't worry though, plug in the recharging cable into your PSP so the battery doesn't run out half way through and follow the instructions exactly, you shouldn't go wrong and as long as the files are from there, you're safe.

Once you've installed 3.03 OE-A, go back to the homepage and download 3.03 OE-B and do the same with this. This is easier to install as it's just a patch. Follow the instructions carefully again (even though there's little you'll need to do) and you'll be fine.

I hope that helps you out, any problems just ask and if I'm online I'll see what help I can give, I'm sure plenty of others will be glad to help as well, though.

Good luck with your PSP!

PS:

REMEMBER, if you're not 100% sure, don't take the risk. I will say, however, I think as long as you follow the given instructions from Dark_Alex, it is probably safer than using an easy installer because you can see exactly what files are going where and by getting the files from his website, you can be sure they're safe. You'll also gain the experience of installing the custom firmware first-hand, which is always a plus.